How to Build a Cinder Block Garage
Cinder blocks and their cousins, concrete blocks, are also known as concrete masonry units (CMUs). They are nominally 8 inches by 8 inches square by 16 inches long. The actual dimensions are 7 5/8 by 7 5/8 by 15 5/8 to allow for mortar joints. Cinder blocks may be installed with mortar joints or with a dry-stack technique, in which blocks are laid firmly together without mortar, then sealed with a surface bonding agent. Dry-stacking is far easier for a do-it-yourselfer. Does this Spark an idea?
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Things You'll Need
- Wood stakes
- Builder's twine
- Tape measure
- Excavator
- Shovel
- Gravel
- Concrete
- Level
- Cinder blocks, including corner and door jamb blocks
- Mortar
- Trowel
- Reinforcing bars
- 2-inch by 4-inch boards
- Roof beams and trusses
- Roof decking and shingles
- 2-inch by-6-inch door framing
- Garage dooor
Instructions
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Design a garage to the dimensions of the cinder blocks. The blocks will alternate at wall corners with long side on short side and vice versa. Once you have a plan, lay out the garage with wood stakes and builder's twine, adding eight inches to the finished dimensions all around for space for concrete footings. Dig a footing trench 16 inches wide and 12 inches deep inside that perimeter.
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Put four inches of gravel in the footings trench and compact it firmly with a hand tamper. Then, pour eight inches of prepared concrete on top, leveling it with a long board. Make sure the footings are the same height and level all the way around the garage perimeter. Put 12-inch sections of reinforcing bar upright in the concrete every four feet and at the corners. Let the concrete cure for a couple of days.
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Lay the first course of cinder blocks in mortar on the footings. Put mortar only under the blocks and just set the blocks firmly flush at the side joints. Run a string outside the perimeter all the way around the garage to indicate straight and level lines for the blocks. Let the first course of blocks set overnight. Place block holes over the rebars where they are installed.
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Add other courses, setting blocks tightly together and alternating blocks, so the joints between them are staggered on all walls. Use special corner blocks for corners and door jamb blocks for the garage door opening. Check regularly to make sure the blocks are plumb and level. Lay blocks to the desired height.
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Solidify the walls by coating them with 1/8 inch of surface bonding cement applied with a trowel. Set reinforcing bars in block hollows every four feet on each wall and at all corners and door opernings. Fill those spaces with concrete. Put upright anchor bolts in the concrete to hold the beams for the roof trusses.
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Fasten beams atop all walls with the anchor bolts. Install roof trusses nailed to the beams and add roof sheathing and shingles. Excavate the interior of the garage eight inches deep, lay down four inches of compacted gravel and pour a 4-inch concrete floor. Level concrete with a 2-by-4 and smooth with a trowel. Add wood framing around the door opening, nail a top plate to the roof beam and use concrete nails or screws to fasten side boards. Install a garage door in that opening.
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Tips & Warnings
Fill all holes in blocks with concrete, if desired, for extra strength.
